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J C Jones

Publications and source records attributed to J C Jones.

At least 37 records · Page 2Linked to original sources
PubMed2000

Antenatal dexamethasone and the growth hormone-insulin-like growth factor axis.

Dexamethasone administration has marked effects on the growth hormone-insulin-like growth factor axis (GH-IGF) in animal and human studies. During pregnancy in the rat, it is associated with fetal growth restriction due to inhibition of IGF bioactivity. In the human only repeated dosages have been associated with fetal growth restriction. The aim of this study is to test the hypothesis that antenatal dexamethasone administration to pregnant women is associated with reduced activity of the GH-IGF axis. To achieve this blood samples were taken from 12 pregnant women pre- and at 24 h and 48 h after dexamethasone administration. In these samples GH, IGF-I, IGF bioactivity and IGF binding protein (IGFBP)-3 protease activity were measured. In view of the interaction between insulin and the GH-IGF axis, glucose and insulin concentrations were also measured. There were no significant differences between the concentrations of GH, IGF-I, IGF bioactivity and IGFBP-3 protease activity before and after dexamethasone. The concentrations of glucose and insulin were significantly higher at 24 h, but not 48 h post-dexamethasone. It is concluded that a single antenatal course of dexamethasone does not alter the GH-IGF-I axis in pregnant women at the time points studied.

Adult↗
PubMed2000

Human bronchial epithelial cells secrete laminin 5, express hemidesmosomal proteins, and assemble hemidesmosomes.

Epithelial cells attach to the basement membrane through adhesive contacts between the basal cells of the epithelium and the proteins of the extracellular matrix (ECM). The hemidesmosome (HD) is a specialized cell-ECM contact, that mediates the attachment of the epithelial cell basal surface to the ECM. In bronchial epithelial cells, the protein components that constitute the HD have not been demonstrated. Using immunohistochemical techniques, we determined that normal human bronchial epithelial (NHBE) cells express the HD cell surface integrin alpha6beta4 and produce laminin 5, the ECM protein associated with HDs. Furthermore, expression of the HD-associated structural proteins, bullous pemphigoid antigens 1 (BPAG 1) and 2 (BPAG 2), was demonstrated in NHBE cells by immunofluorescence microscopy and immunoblot analyses. In addition, we confirmed the presence of laminin 5 in the basement membrane (BM) of bronchial epithelial biopsy specimens and of BP230, BP180, and the alpha6beta4 integrin heterodimer at the site of bronchial epithelial cell-ECM interaction in vivo. Finally, using electron microscopy, we were able to demonstrate intact HDs in a glutaraldehyde-fixed NHBE cell monolayer. These findings suggest that bronchial epithelium forms HDs and that the laminin 5-alpha6beta4 integrin interaction may be important in stabilizing epithelial cell adhesion to the BM in the lung.

Autoantigens↗
PubMed1999

Imidazoline receptor antisera-selected cDNA clone and mRNA distribution.

A novel cDNA, designated Imidazoline Receptor Antisera-Selected cDNA-1 (iras-1), encodes a 167-kD protein. Two of its predicted peptides (42-43 kD) are immunologically consistent with a previously reported 1(1)-imidazoline binding protein. In the present study, two forms of iras mRNA (6.0 and 9.5 kb) were quantified across fresh rat tissues. Highest levels were found in brain (almost exclusively 6.0 kb in size), followed by liver and lung (9.5 > or = 6.0 kb iras mRNA), kidney (6.0 > 9.5 kb), heart (6.0 kb), spleen (6.0 > or = 9.5 kb), testes (6.0 > 9.5 kb), and skeletal muscle (6.0 > 9.5 kb). A correlation exists (p = 0.71, p = 0.05) between total (6.0 + 9.5 kb) iras mRNA and I1 BMAX values across rat tissues, corrected for housekeeping gene expression. Thus, total iras mRNA appears to be roughly proportional to the density of I1-imidazoline binding sites.

Animals↗
PubMed1999

A fluid filtration and clearing technique to assess microleakage associated with three dentine bonding systems.

OBJECTIVES: The aims of this in vitro study were to (a) measure fluid flow through teeth restored with one of three dentine bonding systems and a resin composite restoration; (b) measure the distribution of a silver tracer through the same teeth, and make a comparison with fluid flow; and (c) investigate the effect of thermocycling on both measurement types. METHODS: Coronal segments of 30 premolars, randomly allocated to three equal groups, were assessed by fluid filtration. Each group was restored with a resin composite restoration in conjunction with Fuji Bond LC (FBLC), Scotchbond Multi-Purpose Plus (SMP+) or Prime&Bond 2.1 (P&B2.1). Fluid filtration rates were measured in the intact crown and then after cavity preparation, conditioning, dentine bonding, restoration and at 2 and 24 h, 1 week and 1 month following restoration. Six specimens from each group were thermocycled at 1 week. After final filtration measurements the specimens were perfused with silver nitrate and cleared before scoring tracer penetration. RESULTS: No significant differences (P > 0.05) in fluid filtration rates were found amongst the different bonding systems or at any restoration stage. Thermocycling was not associated with any significant (P > 0.05) increase in fluid filtration. Final fluid filtration and tracer distribution showed a weak and not statistically significant correlation (P > 0.05). The penetration of silver stain indicated a failure of the restorations to seal the cavity and demonstrated a possible pathway by which in vivo post-operative sensitivity could occur. CONCLUSIONS: Although not statistically significant, conditioning of the cavity increased the dentinal permeability but this effect was variable. Thermocycling had no statistically significant effect on microleakage.

Analysis of Variance↗
PubMed1999

Advanced imaging concepts: a pictorial glossary of CT and MRI technology.

This article serves as an illustrative glossary of concepts related to computed tomography (CT) and magnetic resonance imaging (MRI) technology. The principles of tomography, digital processing, image resolution, CT windowing, CT gray levels, contrast enhancement, and MRI spin echo pulse sequences are reviewed. Techniques not commonly described for use in animal patients are also introduced, and include gradient echo, short time of inversion recovery, fluid attenuated inversion recovery and fat saturation pulse sequences, fast imaging, MRI angiography, perfusion and diffusion imaging, brain activation, CT angiography/functional CT, interventional procedures, and three-dimensional CT.

Animals↗
PubMed1999

NC1 domain of type VII collagen binds to the beta3 chain of laminin 5 via a unique subdomain within the fibronectin-like repeats.

Type VII collagen, the major component of anchoring fibrils, consists of a central collagenous triple-helical domain flanked by two noncollagenous, globular domains, NC1 and NC2. Approximately 50% of the molecular mass of the molecule is consumed by the NC1 domain. We previously demonstrated that NC1 binds to various extracellular matrix components including a complex of laminin 5 and laminin 6 (Chen et al, 1997a). In this study, we examined the interaction of NC1 with laminin 5 (a component of anchoring filaments). Both authentic and purified recombinant NC1 bound to human and rat laminin 5 as measured by enzyme-linked immunosorbant assay and by binding of 125I-radiolabeled NC1 to laminin 5-coated wells, but not to laminin 1 or albumin. NC1 bound predominantly to the beta3 chain of laminin 5, but also to the gamma2 chain when examined by a protein overlay assay. The binding of 125I-NC1 to laminin 5 was inhibited by a 50-fold excess of unlabeled NC1 or de-glycosylated NC1, as well as a polyclonal antibody to laminin 5 or a monoclonal antibody to the beta3 chain. In contrast, the NC1-laminin 5 interaction was not affected by a monoclonal antibody to the alpha3 chain. Using NC1 deletion mutant recombinant proteins, a 285 AA (residues 760-1045) subdomain of NC1 was identified as the binding site for laminin 5. IgG from an epidermolysis bullosa acquisita serum containing autoantibodies to epitopes within NC1 that colocalized with the laminin 5 binding site inhibited the binding of NC1 to laminin 5. Thus, perturbation of the NC1-laminin 5 interaction may contribute to the pathogenesis of epidermolysis bullosa acquisita.

Animals↗
PubMed1999

A cell signal pathway involving laminin-5, alpha3beta1 integrin, and mitogen-activated protein kinase can regulate epithelial cell proliferation.

Laminin-5 (LN5) is a matrix component of epithelial tissue basement membranes and plays an important role in the initiation and maintenance of epithelial cell anchorage to the underlying connective tissue. Here we show that two distinct LN5 function-inhibitory antibodies, both of which bind the globular domain of the alpha3 subunit, inhibit proliferation of epithelial cells. These same antibodies also induce a decrease in mitogen-activated protein kinase activity. Inhibition of proliferation by the function-perturbing LN5 antibodies is reversed upon removal of the antibodies and can be overcome by providing the antibody-treated cells with exogenous LN5 and rat tail collagen. Because epithelial cells use the integrin receptor alpha3beta1 to interact with both LN5 and rat tail collagen, we next investigated the possibility that integrin alpha3beta1 is involved in mediating the proliferative impact of LN5. Proliferation of human epithelial cells is significantly inhibited by a function-perturbing alpha3 integrin antibody. In addition, antibody activation of beta1 integrin restores the proliferation of epithelial cells treated with LN5 function-perturbing antibodies. These data indicate that a complex comprising LN5 and alpha3beta1 integrin is multifunctional and contributes not only to epithelial cell adhesion but also to the regulation of cell growth via a signaling pathway involving mitogen-activated protein kinase. We discuss our study in light of recent evidence that LN5 expression is up-regulated at the leading tips of tumors, where it may play a role in tumor cell proliferation.

Animals↗
PubMed1999

The alpha3 laminin subunit, alpha6beta4 and alpha3beta1 integrin coordinately regulate wound healing in cultured epithelial cells and in the skin.

Previously, we demonstrated that proteolytic processing within the globular domain of the alpha3 subunit of laminin-5 (LN5) converts LN5 from a cell motility-inducing factor to a protein complex that can trigger the formation of hemidesmosomes, certain cell-matrix attachment sites found in epithelial cells. We have prepared a monoclonal antibody (12C4) whose epitope is located toward the carboxy terminus of the globular domain of the alpha3 laminin subunit. This epitope is lost from the alpha3 subunit as a consequence of proteolytic processing. Antibody 12C4 stains throughout the matrix of cells that fail to process the alpha3 laminin subunit, but does not recognize the matrix of confluent cultures of MCF-10A cells, which efficiently process their alpha3 laminin chain. In subconfluent populations of MCF-10A cells, 12C4 only stains matrix deposited at the outer edges of cell colonies. In these cells, integrin alpha3beta1 occasionally colocalizes with the staining generated by the 12C4 antibody but alpha6beta4 integrin does not. In wounded MCF-10A cell cultures, the 12C4 antibody stains the extracellular matrix beneath those cells at the very edge of the cellular sheet that moves to cover the wound site. A similar phenomenon is observed in human skin wounds, since we also detect expression of the unprocessed alpha3 laminin subunit at the leading tip of the sheet of epidermal cells that epithelializes skin wounds in vivo. In addition, using alpha3 laminin subunit and integrin function-inhibiting antibodies, we provide evidence that LN5 and its two integrin receptors (alpha6beta4 and alpha3beta1) appear necessary for wound healing to occur in MCF-10A cell culture wounds. We propose a model for healing of wounded epithelial tissues based on these results.

Antibodies, Monoclonal↗
PubMed1998

Mode of adsorption and orientation of an extracellular matrix protein affect its cell-adhesion-promoting activity.

Cell adhesion to extracellular matrix contributes to the organization of tissues and modulates cell behavior. In conventional cell adhesion assays, plastic wells are coated with matrix proteins and assayed for their adhesion-promoting activity. We show here that factors such as sample composition, coating buffers, and manufacturers' plastic treatment markedly affect cell adhesion to the extracellular matrix protein laminin-5 (Ln-5). These factors were shown to affect adsorption efficiency as determined by measuring total adsorbed protein with a polyclonal anti-Ln-5 antiserum. They also influence the availability of the epitope for an adhesion-blocking anti-Ln-5 monoclonal antibody, suggesting that coating conditions affect the orientation of Ln-5. Generally, cell adhesion correlates more strongly with the availability of the epitope for the adhesion-blocking antibody than with total adsorbed Ln-5. Our data further indicate that cell adhesion to other matrix proteins may be influenced by similar factors. Adding Ln-5 samples to plastic wells that had been precoated with non-adhesion-blocking anti-Ln-5 antibodies made cell adhesion independent of factors such as sample composition, coating buffers, and source of plastic. Thus, the control of adsorption efficiency and orientation of extracellular matrix proteins is essential for creation of reliable and reproducible conditions in cell adhesion assays.

Adsorption↗
PubMed1998

A novel model of inflammatory bowel disease: mice deficient for the multiple drug resistance gene, mdr1a, spontaneously develop colitis.

The murine multiple drug resistance (mdr) gene, mdr1a, encodes a 170-kDa transmembrane protein that is expressed in many tissues including intestinal epithelial cells, a subset of lymphoid cells and hematopoietic cells. We report that mdr1a knockout (mdr1a-/-) mice are susceptible to developing a severe, spontaneous intestinal inflammation when maintained under specific pathogen-free animal facility conditions. The intestinal inflammation seen in mdr1a-/- mice has a pathology similar to that of human inflammatory bowel disease (IBD) and is defined by dysregulated epithelial cell growth and leukocytic infiltration into the lamina propria of the large intestine. Treating mdr1a-/- mice with oral antibiotics can both prevent the development of disease and resolve active inflammation. Lymphoid cells isolated from mice with active colitis are functionally reactive to intestinal bacterial Ags, providing evidence that there is enhanced immunologic responsiveness to the normal bacterial flora during IBD. This study is the first description of spontaneous colitis in a gene knockout mouse with an apparently intact immune system. This novel model of spontaneous colitis may provide new insight into the pathogenesis of IBD, the nature of dysregulated immune reactivity to intestinal bacterial Ags, and the potential functional role of mdr genes expressed in the cells and tissues of the colonic microenvironment.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Characterization of a partial cDNA clone detected by imidazoline receptor-selective antisera.

A cDNA clone has been isolated from a human hippocampal cDNA expression library by relying on the selectivity of two antisera that are specific for imidazoline binding proteins. A 1789 bp cDNA clone was sequenced and shown to contain a single open-reading frame that predicts a 66 kDa polypeptide, but it is truncated based on its lack of a stop codon and poly-A+ tail. Two regions of homology exist for the predicted amino acid sequence in common with chromogranin-A and B proteins, a zinc finger protein, and the ryanodine receptor. Northern blot analyses of poly-A+ mRNA from 36 human tissues indicated two differentially expressed transcripts of 6.0 and 9.5 kb. The 6.0 kb mRNA form was enriched in brain and endocrine tissues as compared to other tissues, but not in strict concordance with I1-imidazoline binding sites. The highest overall amounts of the combined transcripts were found in pituitary. In situ hybridization histochemistry revealed an enrichment of the message in neuronal cell bodies of the rat hippocampus and cerebellar cortex. This clone has some of the properties expected of an imidazoline receptor.

Amino Acid Sequence↗
PubMed1998

Processing of laminin-5 and its functional consequences: role of plasmin and tissue-type plasminogen activator.

The laminin-5 component of the extracellular matrices of certain cultured cells such as the rat epithelial cell line 804G and the human breast epithelial cell MCF-10A is capable of nucleating assembly of cell- matrix adhesive devices called hemidesmosomes when other cells are plated upon them. These matrices also impede cell motility. In contrast, cells plated onto the laminin-5-rich matrices of pp126 epithelial cells fail to assemble hemidesmosomes and are motile. To understand these contradictory phenomena, we have compared the forms of heterotrimeric laminin-5 secreted by 804G and MCF-10A cells with those secreted by pp126 cells, using a panel of laminin-5 subunit-specific antibodies. The alpha3 subunit of laminin-5 secreted by pp126 cells migrates at 190 kD, whereas that secreted by 804G and MCF-10A cells migrates at 160 kD. The pp126 cell 190-kD alpha3 chain of laminin-5 can be specifically proteolyzed by plasmin to a 160-kD species at enzyme concentrations that do not apparently effect the laminin-5 beta and gamma chains. After plasmin treatment, pp126 cell laminin-5 not only impedes cell motility but also becomes competent to nucleate assembly of hemidesmosomes. The possibility that plasmin may play an important role in processing laminin-5 subunits is supported by immunofluorescence analyses that demonstrate colocalization of laminin-5 and plasminogen in the extracellular matrix of MCF-10A and pp126 cells. Whereas tissue-type plasminogen activator (tPA), which converts plasminogen to plasmin, codistributes with laminin-5 in MCF-10A matrix, tPA is not present in pp126 extracellular matrix. Treatment of pp126 laminin-5-rich extracellular matrix with exogenous tPA results in proteolysis of the laminin-5 alpha3 chain from 190 to 160 kD. In addition, plasminogen and tPA bind laminin-5 in vitro. In summary, we provide evidence that laminin-5 is a multifunctional protein that can act under certain circumstances as a motility and at other times as an adhesive factor. In cells in culture, this functional conversion appears dependent upon and is regulated by tPA and plasminogen.

Animals↗
PubMed1998

Structure and assembly of hemidesmosomes.

The hemidesmosome is a complex junction containing many proteins. The keratin cytoskeleton attaches to its cytoplasmic plaque, while its transmembrane elements interact with components of the extracellular matrix. Hemidesmosome assembly involves recruitment of alpha 6 beta 4 integrin heterodimers, as well as cytoskeletal elements and cytoskeleton-associated proteins to the cell surface. In our cell culture models, these phenomena appear to be triggered by laminin-5 in the extracellular matrix. Cell interaction with laminin-5 apparently induces both phosphorylation and dephosphorylation of subunits of alpha 6 beta 4 integrin. There is emerging evidence that such events are necessary for subsequent cytoskeleton anchorage to the hemidesmosome cytoplasmic plaque. Once assembled, the hemidesmosome plays an essential role in maintaining firm epithelial adhesion to the basement membrane, with hemidesmosome disruption being a hallmark of certain devastating blistering diseases. However, the hemidesmosome is more than just a stable anchor, as it may also be the site of signal transduction, mediated by its alpha 6 beta 4 integrin component. This review discusses our current knowledge of the structure and assembly of the hemidesmosome.

Animals↗
PubMed1998

In vitro dentinal penetration by tracers used in microleakage studies.

Many microleakage studies, in their methodology, employ different tracers which may penetrate around restorative materials to varying extents due to their physical or chemical characteristics. The present series of in vitro studies were designed to compare the ability of freshly obtained microleakage tracers to enter cut dentinal tubules. Tracers selected were 5% eosin, 2% methylene blue, 50% silver nitrate and Indian ink all buffered, where necessary, to a range of pH 6.9-7.2. The solution of Indian ink was further investigated by particle size analysis to determine the range of particle sizes within the solution. Particles ranged from < 1 micron to 600 microns. Buffered and unbuffered solutions of the tracers were applied for 1 h to open cavities, devoid of a smear layer, prepared in 42 premolars. Specimens were sectioned longitudinally through the cavities either with or without water coolant. Penetration into dentinal tubules by the tracer resulted in an area of stained dentine and this area was subsequently measured using image analysis. The results demonstrated that there were few statistically significant differences between the areas of dentinal penetration associated with each tracer. Neither the tracer used, its pH nor sectioning technique had a predictably significant effect on dentinal penetration. Indian ink was observed to be capable of entering dentinal tubules.

Analysis of Variance↗
PubMed1998

Interaction of BP180 (type XVII collagen) and alpha6 integrin is necessary for stabilization of hemidesmosome structure.

The hemidesmosome is a multimolecular complex that integrates the extracellular matrix with the keratin cytoskeleton and that stabilizes epithelial attachment to connective tissue. A 180 kDa protein (BP180, type XVII collagen), first identified by its reactivity with autoantibodies in the serum of patients with a blistering skin disease called bullous pemphigoid (BP), is a transmembrane component of the hemidesmosome with a collagen-like extracellular domain. Here, using recombinantly expressed molecules and the yeast two-hybrid assay, we have identified alpha6 integrin as a BP180-binding partner. The association between specific domains of the BP180 and alpha6 integrin molecules is inhibited by a 14 mer peptide, whose sequence is identical to amino acid residues 506-519 in the noncollagenous region of the ectodomain of the BP180 molecule, as well as by antibodies raised against this peptide. The 14 mer peptide sequence is part of an epitope recognized by autoantibodies that are pathogenic in BP. In vivo, when 804G cells are plated into medium containing the same peptide, they fail to assemble hemidesmosomes. Furthermore, although BP180 and certain cytoplasmic components of the hemidesmosome colocalize in the peptide-treated cells, they are aberrantly distributed and fail to show extensive association with (alpha6beta4 integrin. Taken together, our results indicate that BP180 is a novel transmembrane ligand of the alpha6beta4 integrin heterodimer. In addition, our data provide support for the possibility that BP180 and alpha6 integrin interaction is not only mediated by the BP epitope but is necessary for hemidesmosome formation.

Antigens, CD↗
PubMed1998

Follicle stimulating hormone (FSH) activates the p38 mitogen-activated protein kinase pathway, inducing small heat shock protein phosphorylation and cell rounding in immature rat ovarian granulosa cells.

This study investigates the possibility that FSH activates the p38 mitogen-activated protein kinase (MAPK) pathway in immature granulosa cells (GC). FSH induced the phosphorylation (activation) of p38 MAPK as evaluated by immunoprecipitation and by phosphorylation-specific immunoblotting. FSH-induced phosphorylation of p38 MAPK was blocked by pretreatment with the protein kinase A (PKA) inhibitor H89 and mimicked by the cAMP generating agonist forskolin, indicating that FSH-induced cAMP production and PKA activation are necessary and sufficient for the activation of p38 MAPK in GC. The small heat shock protein HSP-27 comprises a downstream phosphorylation target for the p38 MAPK pathway. FSH-induced phosphorylation of HSP-27 was blocked by pretreatment with the p38 MAPK inhibitor SB 203580, indicating that p38 MAPK activation is necessary for FSH-induced HSP-27 phosphorylation. FSH-induced GC rounding/aggregation was blocked by pretreatment with SB 203580 indicating that p38 MAPK activation is necessary for FSH-induced GC cell shape change. The results of these experiments show that the p38 MAPK pathway is activated in GC in response to FSH in a cAMP/PKA-dependent manner, and that p38 MAPK activity is required for FSH-induced HSP-27 phosphorylation as well as rounding/aggregation in GC.

Animals↗